The present invention relates to devices for extracting hay or the like from a cylindrical tower silo. The devices are of the kind including a pneumatic conveyor pipe leading centrally into the silo at its upper end, the duct having a suction head to which the material is fed by means of a radial conveyor. Hereinafter, such devices will be referred to as "of the kind described".
In known devices of the kind described, a pneumatic conveyor pipe leads centrally into the circular tower silo and provided with an inlet at its upper end and may be extended and contracted as a telescopic pipe within the silo. The conveyor pipe terminates above the surface of the material in the silo in a suction head to which the material is fed by a conveyor device working outwards from the inside and driven in rotation around the axis of the silo. A system is also known wherein the suction head is allowed to revolve at a distance from the silo axis and around the latter by virtue of a bottom cranked portion of the axial telescopic pipe, in which case the suction head has the material conveyed to it partially from the outside towards the inside and partially from the centre towards the radius of revolution.
In circular tower silos ventable upwards from below, which are loaded with hay (which may be shrivelled or withered), three-quarters of the quantity of material is present between the circle at half the silo radius and the silo periphery, and no more than a quarter of the quantity of material is situated between the axis of the silo and the circle at half the silo radius.
The result is that a conveying operation from the outside towards the inside to the suction head, affecting the large quantities of material situated along the outer annular area of the silo, requires considerable conveying distances.
Consequently, it is an object of the invention to keep the conveying distances for the material which is to be extracted, to the suction head of the pneumatic conveyor duct, to a minimum.